Implement playlist edit feature

* Display playlists as links in index
* Move playlist form in a partial

features/playlists.feature

@@ -16,3 +16,11 @@ Feature: Playlists
     And I fill in "Name" with "Electro"
     And I press "Create"
     Then I should see "Electro" within "ul>li"
+
+  Scenario: Edit playlist
+    Given a playlist named Electro
+    And I am on the playlists page
+    When I follow "Electro"
+    And I fill in "Name" with "Rock"
+    And I press "Save"
+    Then I should see "Rock"

features/step_definitions/playlists_step.rb

@@ -2,3 +2,7 @@ Given /^Foo and Bar playlists$/ do
   @foo = Playlist.create!(:name => 'Foo')
   @bar = Playlist.create!(:name => 'Bar')
 end
+
+Given /^a playlist named Electro$/ do
+  Playlist.create!(:name => 'Electro')
+end